Fill medium saucepan half full with water and bring to a boil. Add green beans and fennel slices; cook until beginning to become tender, about 4 minutes. Pour into a colander to drain and run under cold water to stop the cooking process.

Return the pan to the stove over medium heat. Add olive oil, green beans and fennel. Season with basil, salt and pepper; cook and stir until coated and warm. Transfer to a serving dish and toss with feta cheese.